DE 102 27 032 A1 discloses a modularly constructed online-analyzer. Online analyzers are used for, among other applications, monitoring and optimizing the cleaning performance of clarification plants, monitoring activation basins and flow from a clarification plant, or in the control of filling material metering. Preferably, they monitor the amount of ammonium, phosphate or nitrate in a sample. Analysis of a sample is done, in such case, using known methods of measurement. Corresponding measuring devices for analysis of measurement samples are marketed and distributed by the present assignee.
An essential advantage of online analyzers is that they provide, over longer periods of time, at defined intervals, measured data as regards a monitored process variable. They are able e.g. to provide daily curves of data. Daily curves of data provide reliably, on the one hand, desired information as regards the ongoing operation of a plant; on the other hand, information as regards possibly required changes in the chemical engineering of the plant become available. On the basis of the analysis data, for instance, significant savings in operating equipment and costs accrue.
The online analyzer described in DE 102 27 032 A1 contains at least the following exchangeable modules:                A function module, which is embodied in such a manner that it provides measurement signals, which represent at least one physical or chemical, process variable; the function module is, for example, an ion-selective measuring apparatus or a colorimetric measuring apparatus. The colorimetric measuring apparatus is either a photometer or a spectrometer;        a pump module, which is embodied in such a manner that it supplies, into the function module in predetermined cycles, depending on the particularly applied function module, a predeterminable sample quantity and/or a predeterminable amount of at least one reagent or a predeterminable amount of a cleaning agent; and        an electronics module, which controls the working cycles of the particularly applied pump module and/or the particularly applied function module, evaluates the measurement signals delivered by the function module, and provides the corresponding analysis data for the sample.        
The known solution makes possible change or replacement of individual modules dedicated to the desired measurement parameters and measurement methods, in order to implement the most varied of analyzer types with a minimum number of different modules. Also known from the cited state of the art is to arrange a cooling module in the housing of the online analyzer for cooling reagents and/or the sample, as required.
Moreover, from U.S. Pat. No. 5,587,926, a cooled sampler is known, in the case of which the compressor of the cooling unit is arranged in the upper region of the housing of the sampler. Such an arrangement is to achieve that the cooled region of the housing, in which the samples are stored, is not influenced by the heated air cast off from the compressor. By integrating the cooling unit in the sampler, it becomes well suited for outside setups in the immediate vicinity of the sample-taking location. Disadvantageous in the known solution is that the operator has to decide already when ordering the sampler whether cooling is needed or not; a later changing or retrofitting is no longer possible or possible only with considerable technical and financial sacrifice. Disadvantageous also is that, in the case of a defective cooling unit, the complete housing must be replaced; at least, however, individual components of the cooling unit must be exchanged.
Also known is to install analyzers, for the purpose of cooling, in enclosures or measurement houses, which are air-conditioned. It has also been attempted to avoid this quite expensive solution by providing the analyzers in the form of immersible or submersible probes. Immersible or submersible probes have, however, the disadvantage that they are relatively difficult to maintain, due to dirtying by the medium and due to the handling in the immediate environment of the medium.